Republican efforts to replace President Barack Obama’s Affordable Care Act would devastate children’s hospitals across California and make it harder for millions of people — young and old — to get the care they need, Sen. Dianne Feinstein said in San Francisco Friday.

The GOP plan before the Senate “provides tax cuts for the very wealthy” at the expense of health care for children, Feinstein told an audience of about 100 doctors, nurses, health care professionals and parents of patients at UCSF Benioff Children’s Hospital San Francisco. “I don’t know who would want that type of a tax cut.”

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Feinstein joined hospital officials on a morning tour of the sprawling Mission Bay facility, talking with doctors, nurses, parents and patients, before returning for a 45-minute pep rally aimed at revving up opposition to the GOP attack on the Affordable Care Act.

There’s still time to make a difference, Feinstein said.

“I’m going back (to Washington) Sunday and see if the bill comes to the floor Monday,” Feinstein said. “If it doesn’t, it doesn’t have the votes yet. We need to mobilize and call everyone you know.”

The focus of concern is the GOP effort to trim Medicaid, which Obama’s 2010 health care plan expanded to cover millions more people.

That includes more than 3 million of the 14 million people now covered in California, where the program is known as Medi-Cal.

State officials say California could lose $30 billion a year in federal Medi-Cal funds by 2027 and $114 million annually by 2037.

“Medi-Cal is not just for the poor,” said Mark Laret, chief executive officer of UCSF Health. “One out of every two births in the country is on Medicaid. We’re talking about your elderly parents in nursing homes.”

In California, more than one-third of the state’s 39 million residents are on Medi-Cal, along with 1 out of every 2 children, 60 percent of nursing home residents and half the people with disabilities.

While 27 percent of San Franciscans (230,000 residents) are on Medi-Cal, that pales when compared with the 40 percent in Los Angeles County (4.1 million people) and the 50 percent in Fresno County (500,000 people).

It’s not just people who got a boost from the Medi-Cal expansion, said Sam Hawgood, UCSF chancellor. The additional money is a boon to California hospitals, which now receive money from recently covered patients who previously would have been treated for free.

Even with the Medi-Cal expansion, the program still doesn’t cover all medical costs. UCSF last year spent $289 million on uncompensated care for Medi-Cal patients, he said, a number that would soar if the program is trimmed.

That’s a special concern for children’s hospitals, since many of their young patients are on Medi-Cal. At UCSF’s Benioff Children’s Hospital San Francisco, it’s 50 percent. At its sister hospital in Oakland, 70 percent of the patients are on Medi-Cal.

“Kids will suffer if this (bill) goes through,” said Dr. Michael Anderson, president of the UCSF Benioff Children’s Hospitals.

Feinstein also heard from three parents, who she described as “true American warrior women,” who talked about what the children’s hospital — and the Medi-Cal money to pay for needed care — meant to their children.

Two of them spoke alongside Feinstein. Kristin Chaset talked about her nearly 2-year-old daughter, Megan, who had heart surgery five hours after birth and spent more than 10 months in the hospital before finally going home to continuing nursing care and therapy.

Sally McDonald spoke of her daughter, Maggie, who underwent 80 surgeries for a congenital disorder, but was provided the resources that enabled her to graduate from Mission High School before she died at age 20.

“There is no nice way to put this,” McDonald said. The proposed health care bill “will be fatal to many children.”

In a statement Thursday, Feinstein called the GOP health plan “an immoral policy.” Pressed on that Friday, she pointed to the women who told the stories of their children.

“Listen to these women,” the senator said. Their children “had the chance to live the life they had,” something she suggested likely wouldn’t happen if the proposed Medicaid cuts went through.